An NIR-II light responsive antibacterial gelation for repetitious photothermal/thermodynamic synergistic therapy

Drug-resistant bacterial infection is a serious threat to the survival and health of human. Clinically, the conventional therapy for subcutaneous infections generally involves the systemic administration of high dose of antibiotics and frequently causes detrimental side effects in normal tissues. To overcome this issue, an acidity-responsive near infrared (NIR) light-triggered injectable hydrogel was designed for non-antibiotic local treatment. Herein, poly(ethylene glycol) diacrylate (PEGDA) was used as hydrogel matrix, polyoxometalate (POM) as acidity-enhanced photothermal agent and 2,2′-azobis[2-(2-imidazolin-2-yl) propane] dihydro-chloride (AIPH) as thermo-responsive initiator. After the hydrogel precursor solution (AIPH/POM/PEGDA) was injected into the acidic infected tissue, the aggregated POM with strong photothermal property was restricted to the site of abscess. Upon excitation at 1060 nm laser, the heat generated from POM would trigger alkyl radical formation from AIPH and thereafter achieving NIR-triggered in situ gel. Consequently, the POM and AIPH were trapped in Gel(AIPH/POM) and exhibited long-term retention in the abscess for further repeated local photothermal/thermodynamic antibacterial therapy. In vitro antibacterial evaluation indicated that the system could effectively eradicate drug-resistant bacteria through destroying bacteria integrity and producing the noxious alkyl radical under NIR light illumination. Moreover, the bacterial burden of abscess was significantly relieved and more collagens were deposited after the administration of Gel(AIPH/POM) and repeated NIR light. Meanwhile, no apparent adverse effect was observed during the treatment. This work not only provides a light-triggered gelation for local photothermal/thermodynamic synergistic therapy, but also offers a novel strategy for the rational design of light-responsive intelligent antibacterial hydrogels.